Box plot of non-synonymous site divergence/synonymous site divergence ( d
) distributions for genes classified into gonadal or non-gonadal categories in the embryonic and adult stages based on expressed sequence tag (EST) data. Classification of genes using a greater than twofold proportion of representation relative to other stages is shown. Inset indicates d
S distributions when adult stage gonads are separated into ovary and testis. Genes classified into the adult gonads category are evolving more rapidly than all other categories (P < 0.01) though this is only the case for the adult testis category when the gonads are classified separately. In contrast, genes classified in the embryonic gonads category are evolving less rapidly than all other categories (P < 0.05). Non-gonadal embryonic and adult tissues show no significant differences in their rates of evolution (P > 0.05). AGe = adult general; AOv = adult ovary; ATe = adult testis; EGe = embryonic general; EGo = embryonic gonads.